Surface acoustic wave code generator

• US 3,869,682 A
• Filed: 04/10/1974
• Issued: 03/04/1975
• Est. Priority Date: 05/03/1973
• Status: Expired due to Term

• Current Assignee: John Josiah Crisp, John Stuart Heeks
• Original Assignee: John Josiah Crisp, John Stuart Heeks
• Inventors: Heeks, John Stuart, Crisp, John Josiah
• Primary Examiner(s): Brody, Alfred L.
• Application Number:
  US05/459,506
• Time in Patent Office: 328 Days
• Field of Search: 332/11R,11D,16R,16T,18,19,26 307/260,262,293 333/3R
• US Class Current: 708/250
• CPC Class Codes: G06F 2207/581 Generating an LFSR sequence, e.g. an m-sequence; sequence may be generated without LFSR, e.g. using Galois Field arithmetic
• CPC Class Codes: G06F 2207/583 Serial finite field implementation, i.e. serial implementation of finite field arithmetic, generating one new bit or trit per step, e.g. using an LFSR or several independent LFSRs; also includes PRNGs with parallel operation between LFSR and outputs
• CPC Class Codes: G06F 7/584 using finite field arithmetic, e.g. using a linear feedback shift register

Abstract

There is disclosed a phase shift modulated pseudo-noise code generator. This generator employs a surface acoustic wave tapped delay line with feedback. A radio frequency phase reference signal is provided at the tapping points. The radio frequency phase of the modulated carrier is compared with the radio frequency phase of the reference signal at each tapping point from which the feedback is derived. The comparison is performed in a surface acoustic wave modulo-2 adder. This comparison overcomes the phase shift due to temperature effects.

Claims

1. A binary code generator comprising:

a first surface acoustic wave tapped delay line;

first means for generating clock signals having a repetition rate equal to the binary code bit rate;

second means coupled to said first means and said first delay line for inserting phase modulated RF signals into the input of said first delay line, said second means being under control of said clock signals;

third means coupled to said first delay line to derive first and second output signals from first and second tapping points of said first delay line;

fourth means to derive for said first and second tapping points first and second phase reference signals by which the RF phase of said first and second output signals of said first and second tapping points can be checked;

fifth means coupled to said first and second tapping points and said fourth means to compare said first and second output signals with respect to said first and second phase reference signals resulting in third and fourth output signals;

sixth means coupled to said fifth means to perform a modulo-2 addition of said third and fourth output signals resulting in a fifth output signal; and

seventh means coupled to said sixth means to apply said fifth output signal as a feedback signal to said second means to modify said phase modulation of said phase moduLated RF signals.

2. A generator according to claim 1, further including an output transducer for said first delay line;

and wherein said second means includes an input transducer for said first delay line;

each of said input and output transducers is an interdigital transducer.

3. A generator according to claim 2, wherein each of said first and second tapping points is a single-finger-pair transducer.

4. A generator according to claim 1, wherein said fourth means includes a second surface acoustic wave tapped delay line parallel to said first delay line, said second delay line having a third tapping point corresponding to said first tapping point and a fourth tapping point corresponding to said second tapping point, an eighth means coupled to said second delay line for inserting therein RF signals modulated by said clock signals, and ninth means coupled to said second delay line to derive said first and second phase reference signals.

5. A generator according to claim 4, wherein said second delay line is fabricated identical to said first delay line.

6. A generator according to claim 4, wherein each of said third and fourth tapping points is a single-finger-pair transducer.

7. A generator according to claim 6, further including an output transducer for said second delay line;

and wherein said eighth means includes an input transducer for said second delay line;

each of said input and output transducers is an interdigital transducer.

8. A generator according to claim 7, wherein each of said first and second tapping points is a single-finger-pair transducer.

9. A generator according to claim 8, further including an output transducer for said first delay line;

and wherein said second means includes an input transducer for said first delay line;

each of said input and output transducers is an interdigital transducer.

10. A generatoor according to claim 4, wherein said second delay line includes an input transducer identical to an input transducer for said first delay line, an output transducer identical to an output transducer of said first delay line, said first and third tapping point having a first tapping point transducer common to said first and second delay lines, and said second and third tapping point having a second tapping point transducer common to said first and second delay lines.

11. A generator according to claim 1, wherein said first and second phase reference signals are the same as said first and second output signals but said first and second phase reference signals have a delay difference equal to one bit period from the associated one of said first and second output signals.

12. A generator according to claim 11, wherein said third means includes eighth means to derive sixth and seventh output signals from third and fourth tapping points each disposed adjacent a different one of said first and second tapping points, said sixth and seventh output signals being said first and second phase reference signals.

13. A generator according to claim 11, wherein said third means includes eighth means to derive from said first and second output signals sixth and seventh output signals each being a different one of said first and second output signals having a delay equal to one bit period, said sixth and seventh output signals being said first and second phase reference signals.

14. A generator according to claim 13, wherein said fifth means includes eighth means to perform a modulo-2 addition of said first output signals and one of said sixth and seventh output signals, and ninth means to perform a modulo-2 addition of said second output signal and the other of said sixth and seventh output signals.

15. A generator according to claim 14, wherein each of said eighth and ninth means includes a surface acoustic wave device having a first interdigital Input transducer to which the associated one of said first and second output signals is applied, a second interdigital input transducer to which the associated one of said sixth and seventh output signals is applied and an interdigital output transducer disposed intermediate said first and second input transducers;

the distance between said output transducer and one of said first and second input transducer being larger, by an amount equal to the distance between two adjacent delay line tapping points, than the distance between said output transducer and the other of said first and second input transducers.

16. A generator according to claim 1, wherein said fifth means includes eighth means to perform a modulo-2 addition of said first output signal and one of said first and second phase reference signal, and ninth means to perform a modulo-2 addition of said second output signal and the other of said first and second phase reference signal.

17. A generator according to claim 16, wherein each of said eighth and ninth means includes a surface acoustic wave device having two interdigital input transducers and an output transducer disposed intermediate of and equidistant from said two input transducers.